The invention relates to a switch for signaling changes in the position and accelerations of its housing equipped with a movably mounted permanent magnet and at least one reed switch as active elements, wherein the permanent magnet is suspended in the manner of a pendulum; and the reed switch is disposed below the circle segment described by the pendulum in the effective range of the magnetic field.
Such switches are known per se. They are employed, for example, in motor vehicles where, if a predetermined acceleration or deceleration limit value is exceeded, they are to initiate a switching process, for example, turn on an optical or acoustical signal, inflate a so-called "air bag", or the like. Prior art switches of this type are provided with a mercury switch as the position or acceleration sensitive sensor in which a movably positioned small quantity of mercury short-circuits two electrodes if a predetermined limit value is exceeded.
It is also known to realize the same purpose by replacing the mercury switch with a movably mounted magnet in whose field a reed switch is disposed. If an acceleration or deceleration of predetermined magnitude acts on the magnet, the change in the magnetic field connected therewith causes the reed switch to change its switching state, which can be utilized in the same manner as the switching process of the above-mentioned mercury switch. Position and acceleration sensitive switches equipped with a movably mounted permanent magnet and at least one reed switch as the active elements are disclosed, for example, in German Patent DE 4,032,717.A1. There, the permanent magnet is suspended from a switch housing in the manner of a pendulum. Changes in position and accelerations of the switch housing cause the permanent magnet to move relative to the reference system of the switch housing and in this way, at certain limit values of position change or acceleration, cause a change in the switching state of the reed switch which is stationarily fixed to the switch housing.
Some of the prior art arrangements composed of a permanent magnet and a reed switch are of extremely complicated construction or, because of the arrangement of their active elements, they have a high response threshold or an unduly high hysteresis in their turn-on and turn-off processes.